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Semiconductor Chip Protection during Ultrasonic Machining

IP.com Disclosure Number: IPCOM000081465D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Leighton, WW: AUTHOR

Abstract

This technique protects a chip and the adjacent modular substrate circuitry from slurry abrasion during ultrasonic machining of a closely dimensioned hole through the substrate. The hole is used for testing an electrically powered chip.

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Semiconductor Chip Protection during Ultrasonic Machining

This technique protects a chip and the adjacent modular substrate circuitry from slurry abrasion during ultrasonic machining of a closely dimensioned hole through the substrate. The hole is used for testing an electrically powered chip.

The protective method is to coat the chip with two abrasive-resistant materials. The area immediately beneath the chip is coated, first, with a plastic which is easily removed by a solvent. A second, more rigid coating, is applied over the back of the chip and adjacent the surrounding substrate, thereby anchoring the chip to the module. A polycarbonate, such as LEXAN*, is dissolved by stirring into a suitable solvent such as CH(2)CL(2). The solution is used to cement a long, thinwall glass tube around the chip. The cement is then allowed to dry thoroughly.

The assembly is then tilted approximately 45 degrees and the tube is half filled with the solution of LEXAN. Immediately thereafter the assembly, retained at the same tilt, is placed in a vacuum chamber and held to 10/-1/ atmosphere for 3 minutes. It is then immediately removed, inverted, and he glass tube is pulled away slowly. The dry cement pulls away with the tube, leaving only a small quantity of the LEXAN over the chip. This is dried thoroughly.

In the next step the chip and surrounding substrate area is overlaid with a clear epoxy, such as ARALDITE**, and permitted to harden thoroughly. The chip and associated circ...